Field of the Invention
This disclosure relates to a sheet conveying apparatus conveying a sheet and an image forming apparatus.
Description of the Related Art
In the related art, an image forming apparatus such as a copier, a printer, or a facsimile includes an image forming portion, and a sheet conveying apparatus which conveys sheets to the image forming portion by using conveyance rollers. In the image forming apparatus of the related art, there are cases where a sheet is skewed when the sheet is conveyed due to a conveyance roller being deformed, alignment of the conveyance roller being deviated, or the like. Here, in the image forming apparatus, accuracy of an image forming position considerably depends on a position of a sheet relative to the image forming portion, and thus a major image quality factor is to match a position of the sheet with the image forming portion with high accuracy.
Therefore, in the image forming apparatus of the related art, a skew correction portion is provided in the sheet conveying apparatus, and accuracy of an image forming position is improved by correcting a sheet skew with the skew correction portion. As such a skew correction portion, there is a skew correction portion including a shutter member which is biased by a biasing portion such as a spring in a reverse direction to a direction of sheet conveyance and in which a sheet front end comes into abutment with the shutter member.
As disclosed in Japanese Patent No. 5318221, such a shutter type skew correction portion has been proposed which includes a conveyance roller, a conveyance driven roller, and a plurality of shutter members. The conveyance driven roller is in contact with the conveyance roller. The plurality of shutter members is provided rotatably coaxially with a shaft of the conveyance driven roller and each of the shutter members has a plurality of sheet abutment portions on a peripheral surface thereof. In the skew correction portion with this configuration, if a forefront portion of the front end of a skewed sheet comes into abutment with the sheet abutment portion of one of the plurality of shutter members, the sheet is stopped in a state in which the sheet front end is in contact with the sheet abutment portion by receiving a reaction force from the sheet abutment portion. Then, if the sheet is further conveyed, the sheet is deflected. If the sheet is deflected in this way, the sheet front end comes into abutment with the sheet abutment portions of the plurality of shutter members. Consequently, the sheet skew is corrected, and then the sheet of which the skew has been corrected enters a nip between the conveyance roller and the conveyance driven roller and is conveyed to a downstream side.
Meanwhile, in recent years, there has been a demand for improvement in the productivity, that is, improvement in the number of sheets on which images are formed per unit time in the image forming apparatus. For this reason, a sheet conveyance speed has been increased, or an interval (hereinafter, referred to as an inter-sheet distance) between a rear end of a sheet and a front end of the following sheet, the sheets being continuously conveyed, has been reduced. Due to the increase in a sheet conveyance speed or the reduction in the inter-sheet distance, the shutter member is required to return to a skew correction position within a short inter-sheet distance after a preceding sheet passes.
For example, if a skew of a preceding sheet is corrected, the shutter member of the related art is pushed and rotated by the sheet. When the shutter member is rotated by a predetermined distance, the shutter member is moved by a cam portion to a position where a skew of a sheet which is conveyed next is corrected by the following sheet abutment portion. Even if the shutter member is moved as mentioned above, the following sheet abutment portion is in contact with an upper surface of the conveyed sheet until the rear end of the preceding sheet passes through the sheet abutment portion.
Therefore, the movement of the following sheet abutment portion to the position for correcting a sheet skew is performed after the rear end of the preceding sheet passes the shutter member. Thus, the inter-sheet distance between the preceding and succeeding sheets is required to be set such that the front end of the succeeding sheet does not reach the shutter member during a period from when the rear end of the preceding sheet passes through the shutter member until when the following abutment surface moves to the position for correcting the skew of the sheet.